A substrate processing apparatus is used in the process of manufacturing semiconductors, liquid crystal panels, and the like to supply a treatment liquid (e.g., resist stripping liquid, a rinsing liquid, washing liquid, etc.) to a surface of a substrate, such as a wafer or a liquid crystal substrate, to thereby treat the surface. From the viewpoint of uniformity and reproducibility, the substrate processing apparatus uses a single wafer system in which substrates are processed one by one in a dedicated processing chamber. Besides, in order to standardize the substrate transfer system, substrates are transported as being stored in a common special case (e.g., FOUP, etc.). In this special case, the substrates are stored in such a manner that they are stacked at predetermined intervals.
The substrate processing apparatus uses a substrate transfer apparatus such as a transfer robot. The substrates are taken out from the special case and transported to the processing chamber. After that, the processed substrates are stored in the special case. At this time, the substrate processing is not limited to one type, but a plurality of types of processing steps (e.g., resist stripping step, rinsing step, washing step, etc.) may be each performed in a dedicated processing chamber for each type, and returned to the special case.
The substrate transfer apparatus performs the operation of exchanging processed substrates and unprocessed substrates in the special case, the processing chamber, a buffer in the middle of them, and the like. When exchanging the substrates, the substrate transfer apparatus alternately moves two hands for the processed substrate and the untreated substrate with two arms. That is, two hands are alternately used to exchange the substrates once, and the hands are taken in and out twice. Therefore, the substrates are not transferred efficiently, and the time taken for the substrate transfer is prolonged. This reduces the productivity of the substrate processing apparatus.